For a structured-light based measuring system, if a light beam spot and its corresponding coordinate Z are known, the coordinate of a cross point of the light beam on the surface of an object may be obtained. For this purpose, during the demarcation of the structured-light based measuring system, light beams of the structured-light are designed in such a way that the image distribution of a light beam of the structured-light does not overlap that of a neighboring beam of the structured-light within a camera, and the respective image positions are recorded for various depths (i.e. the coordinates Z). During the practical measurement, it is possible to quickly determine a light beam corresponding to an already known image point in a manner of determining a light beam corresponding to the demarcated image point that is closest to the known image point. An interpolating method may be used for determining 3D coordinates of the known image point. In an existing structured-light based measuring system, for the purpose of ensuring that the image distributions of any two light beams at different depths do not overlap with each other, it is necessary to concentrate the image distribution of each light beam, that is, a small image displacement corresponds to a large physical depth difference, which results in a low measuring precision.